Remove alloc feature

Cargo.toml

@@ -14,8 +14,7 @@ criterion = { version = "0.5", features = ["html_reports"] }
 rand = "0.8"
 
 [features]
-std = [ "alloc"]
-alloc = []
+std = []
 
 [[bench]]
 name = "prime_benches"

src/lib.rs

@@ -107,7 +107,6 @@
 //! # Features
 //!
 //! `std`: derives the [`Error`](std::error::Error) trait for the error types.
-//! `alloc`: enables conversion of the type returned by [`primes_geq`] and [`primes_lt`] into [`Vec`]s and [`Box`]ed slices.
 
 #![forbid(unsafe_code)]
 #![cfg_attr(all(not(test), not(feature = "std")), no_std)]